Linux theme detection fails with `gsettings` Missing on 0.8.1

[luh-05]

Description:

On some Linux installations, theme detection fails due to the absence of gsettings. This issue was observed starting from version 0.8.1 but not in 0.8.0. I suspect this isn't a new bug but rather an existing one that now logs properly due to the introduction of slf4j-simple in #123.

For more information, please see the related issue on this repository.

Steps to Reproduce:

1. Use a Linux system without gsettings installed
2. Run an application using version 0.8.1
3. Observe the logs indicating theme detection failure

Actual Behavior:
Theme detection fails with the following error:
java.io.IOException: Cannot run program "gsettings": error=2, No such file or directory

Expected Behavior:

• The application should gracefully handle the absence of gsettings or even provide an alternative theme detection method

Environment:

• OS: NixOS 24.11.20241105.411656 (Vicuna)
• Kernel: Linux 6.11.5-zen1
• WM: Hyprland
• Java Version: 21

Additional Context:

• Version 0.8.0 does not produce this issue; reverting to it resolves the problem.
• Error logs suggest the issue stems from jSystemThemeDetector
• Example logs from my system when trying to run this assignment:

> Task :Main.main()
[main] ERROR com.jthemedetecor.GnomeThemeDetector - Couldn't detect Linux OS theme
java.io.IOException: Cannot run program "gsettings": error=2, No such file or directory
	at java.base/java.lang.ProcessBuilder.start(ProcessBuilder.java:1170)
	at java.base/java.lang.ProcessBuilder.start(ProcessBuilder.java:1089)
	at java.base/java.lang.Runtime.exec(Runtime.java:681)
	at java.base/java.lang.Runtime.exec(Runtime.java:491)
	at java.base/java.lang.Runtime.exec(Runtime.java:366)
	at com.jthemedetecor.GnomeThemeDetector.isDark(GnomeThemeDetector.java:57)
	at fopbot.GuiPanel.<init>(GuiPanel.java:87)
	at fopbot.KarelWorld.setVisible(KarelWorld.java:363)
	at fopbot.World.setVisible(World.java:28)
	at h03.Main.main(Main.java:17)
Caused by: java.io.IOException: error=2, No such file or directory
	at java.base/java.lang.ProcessImpl.forkAndExec(Native Method)
	at java.base/java.lang.ProcessImpl.<init>(ProcessImpl.java:295)
	at java.base/java.lang.ProcessImpl.start(ProcessImpl.java:225)
	at java.base/java.lang.ProcessBuilder.start(ProcessBuilder.java:1126)
	... 9 more
[main] ERROR com.jthemedetecor.GnomeThemeDetector - Couldn't detect Linux OS theme
Caused by: java.io.IOException: error=2, No such file or directory

java.io.IOException: Cannot run program "gsettings": error=2, No such file or directory
	at java.base/java.lang.ProcessBuilder.start(ProcessBuilder.java:1170)
	at java.base/java.lang.ProcessBuilder.start(ProcessBuilder.java:1089)
	at java.base/java.lang.Runtime.exec(Runtime.java:681)
	at java.base/java.lang.Runtime.exec(Runtime.java:491)
	at java.base/java.lang.Runtime.exec(Runtime.java:366)
	at com.jthemedetecor.GnomeThemeDetector.isDark(GnomeThemeDetector.java:57)
	at com.jthemedetecor.GnomeThemeDetector$DetectorThread.<init>(GnomeThemeDetector.java:111)
	at com.jthemedetecor.GnomeThemeDetector.registerListener(GnomeThemeDetector.java:85)
	at fopbot.GuiPanel.<init>(GuiPanel.java:108)
	at fopbot.KarelWorld.setVisible(KarelWorld.java:363)
	at fopbot.World.setVisible(World.java:28)
	at h03.Main.main(Main.java:17)
Caused by: java.io.IOException: error=2, No such file or directory
	at java.base/java.lang.ProcessImpl.forkAndExec(Native Method)
	at java.base/java.lang.ProcessImpl.<init>(ProcessImpl.java:295)
	at java.base/java.lang.ProcessImpl.start(ProcessImpl.java:225)
	at java.base/java.lang.ProcessBuilder.start(ProcessBuilder.java:1126)
	... 11 more
[GTK Theme Detector Thread] ERROR com.jthemedetecor.GnomeThemeDetector - Couldn't start monitoring process 
java.io.IOException: Cannot run program "gsettings": error=2, No such file or directory
	at java.base/java.lang.ProcessBuilder.start(ProcessBuilder.java:1170)
	at java.base/java.lang.ProcessBuilder.start(ProcessBuilder.java:1089)
	at java.base/java.lang.Runtime.exec(Runtime.java:681)
	at java.base/java.lang.Runtime.exec(Runtime.java:491)
	at java.base/java.lang.Runtime.exec(Runtime.java:366)
	at com.jthemedetecor.GnomeThemeDetector$DetectorThread.run(GnomeThemeDetector.java:121)
Caused by: java.io.IOException: error=2, No such file or directory
	at java.base/java.lang.ProcessImpl.forkAndExec(Native Method)
	at java.base/java.lang.ProcessImpl.<init>(ProcessImpl.java:295)
	at java.base/java.lang.ProcessImpl.start(ProcessImpl.java:225)
	at java.base/java.lang.ProcessBuilder.start(ProcessBuilder.java:1126)
	... 5 more

Deprecated Gradle features were used in this build, making it incompatible with Gradle 9.0.

You can use '--warning-mode all' to show the individual deprecation warnings and determine if they come from your own scripts or plugins.

For more on this, please refer to https://docs.gradle.org/8.10.2/userguide/command_line_interface.html#sec:command_line_warnings in the Gradle documentation.

[Rdeisenroth]

This is sadly expected and a limitation of the library we use for system theme detection, which seems to rely on gnome settings instead of freedesktop implementations:
Dansoftowner/jSystemThemeDetector#45

Personally, it seems to work fine for me on my Hyprland setup, but i do also have gnome settings installed.

I think a sensible workaround would be to read an environment variable like

FOPBOT_FORCE_THEME=dark

to force a desired theme, as a full on implementation with the freedesktop spec seems challenging, especially if we want it to react to live color theme changes... If someone is willing to put in the effort though, it should be possible with something like xdg-java